Typically, a solid oxide fuel cell (SOFC) employs an electrolyte of ion-conductive solid oxide such as stabilized zirconia. The electrolyte is interposed between an anode and a cathode to form an electrolyte electrode assembly (MEA). The electrolyte electrode assembly is interposed between separators (bipolar plates). In use, predetermined numbers of the electrolyte electrode assemblies and the separators are stacked together to form a fuel cell stack.
In the fuel cell, it is required to supply a fuel gas (e.g., hydrogen-gas) to the anode of the electrolyte electrode assembly and an oxygen-containing gas (e.g., the air) to the cathode of the electrolyte electrode assembly. The fuel gas and the oxygen-containing gas also need to be supplied to each of the fuel cells.
As the fuel cell of this type, for example, a flat plate type solid oxide fuel cell as disclosed in Japanese Patent No. 4291299 (hereinafter referred to as Conventional Technique 1) is known. The fuel cell includes, as shown in FIG. 10, a cell stack 1a, and four manifolds M1 to M4 provided around the cell stack 1a. The manifolds M1 to M4 supply, and discharge the fuel gas and the oxygen-containing gas to and from each of unit cells 2a. In the fuel cell, a pressure is applied to the cell stack 1a by a first pressure applying mechanism 3a, and a pressure is applied to each of the manifolds M1 to M4 by a second pressure applying mechanism 4a. 
The cell stack 1a is formed by stacking the unit cells 2a and interconnectors 5a alternately. The manifold M1 serves as a fuel gas supply manifold for supplying the fuel gas to the cell stack 1a, and the manifold M2 serves as a discharge manifold for discharging the fuel gas from the cell stack 1a. The manifold M3 serves as an oxygen-containing gas supply manifold for supplying the oxygen-containing gas to the cell stack 1a, and the manifold M4 serves as a discharge manifold for discharging the oxygen-containing gas from the cell stack 1a. 
The first pressure applying mechanism 3a includes a holder plate 6a and a compression spring 7a provided on the cell stack 1a. The second pressure applying mechanism 4a includes compression springs 8a provided on the manifolds M1 to M4.
Further, as shown in FIG. 11, a solid oxide fuel cell stack disclosed in Japanese Laid-Open Patent Publication No. 2007-317490 (hereinafter referred to as Conventional Technique 2) includes a stack body 2b formed by stacking a plurality of solid oxide fuel cells 1b in a stacking direction, and a pair of outer support members 3b, 4b provided on both sides of the stack body 2b in the stacking direction.
The fuel cell stack has a fuel gas supply hole 5b for supplying the fuel gas, a fuel gas discharge hole 6b for discharging the fuel gas, an air supply hole 7b for supplying the air, and an air discharge hole 8b for discharging the air. The holes 5b to 8b in the fuel cell stack make up an internal manifold.
Bolts 9b are tightly screwed into nuts (not shown) to tighten the outer support members 3b, 4b inwardly in the stacking direction. Thus, the stack body 2b is pressed inwardly by the outer support members 3b, 4b, and components of the fuel cell stack are fixed together.